Radial temperature control for lattice-mismatched epitaxy

Abstract

Methods are disclosed of fabricating a compound nitride semiconductor structure. A substrate is disposed over a susceptor in a processing chamber, with the susceptor in thermal communication with the substrate. A group-III precursor and a nitrogen precursor are flowed into the processing chamber. The susceptor is heated with a nonuniform temperature profile to heat the substrate. A nitride layer is deposited over the heated substrate with a thermal chemical vapor deposition process within the processing chamber using the group-III precursor and the nitrogen precursor.

Description

BACKGROUND OF THE INVENTION[0001]The history of light-emitting diodes (“LEDs”) is sometimes characterized as a “crawl up the spectrum.” This is because the first commercial LEDs produced light in the infrared portion of the spectrum, followed by the development of red LEDs that used GaAsP on a GaAs substrate. This was, in turn, followed by the use of GaP LEDs with improved efficiency that permitted the production of both brighter red LEDs and orange LEDs. Refinements in the use of GaP then permitted the development of green LEDs, with dual GaP chips (one in red and one in green) permitting the generation of yellow light. Further improvements in efficiency in this portion of the spectrum were later enabled through the use of GaAlAsP and InGaAlP materials.[0002]This evolution towards the production of LEDs that provide light at progressively shorter wavelengths has generally been desirable not only for its ability to provide broad spectral coverage but because diode production of shor...

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Benefits of technology

[0006]In some instances, a second nitride layer is deposited after depositing the first nitride layer. A second group-III precursor and a second nitrogen precursor are flowed into the processing chamber. The second group-III precursor comprises a second group-III element. The susceptor is heated with a second nonuniform temperature profile to heat the substrate while flowing the second group-III precursor and the second nitrogen precursor. The second nitride layer is deposited over the first nitride layer and over the heated substrate with a thermal chemical vapor deposition process within the processing chamber using the second group-III precursor and the second nitrogen precursor. The second group-III element may be different from the first group-III element. The second nitride layer may have a different coefficient of thermal expansion than the first nitride layer. The second nonuniform temperature profile may be different from the first nonuniform temperature profile. In such cases, the first nonuniform temperature profile may be changed smoothly to the second nonuniform temperature profile.

[0011]After depositing the first layer, a second layer may be grown. A second process gas is flowed into the processing chamber. The second process gas includes precursors for growth of the second layer over the first layer, with the first layer and the second layer having different coefficients of thermal expansion. The susceptor is heated with a second nonuniform temperature profile different from the first nonuniform temperature profile to heat the substrate while flowing the second process gas. The second layer is deposited over the first layer and over the heated substrate with a thermal chemical vapor deposition process within the processing chamber using the second process gas. The susceptor may be heated with the second nonuniform temperature profile by smoothly changing the first nonuniform temperature profile to the second nonuniform temperature profile.

Problems solved by technology

While some modestly successful efforts had previously been made in the production of blue LEDs using SiC materials, such devices suffered from poor luminescence as a consequence of the fact that their electronic structure has an indirect bandgap.

While the feasibility of using GaN to create photoluminescence in the blue region of the spectrum has been known for decades, there were numerous barriers that impeded their practical fabrication.

These included the lack of a suitable substrate on which to grow the GaN structures, generally high thermal requirements for growing GaN that resulted in various thermal-convection problems, and a variety of difficulties in efficient p-doping such materials.

The use of sapphire as a substrate was not completely satisfactory because it provides approximately a 15% lattice mismatch with the GaN.

While some improvements have thus been made in the manufacture of such compound nitride semiconductor devices, it is widely recognized that a number of deficiencies yet exist in current manufacturing processes.

Moreover, the high utility of devices that generate light at such wavelengths has caused the production of such devices to be an area of intense interest and activity.

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